Railroad impedance bond connection



Sept. CREMER HAL v RAILROAD IMPEDANCE BOND CONNECTION Original Filed Jan. 23, 1953 FIG.]

insula lions insulation FIG 4 }'14 (insulation i9, 10 Mau ham Patented Sept. 17, 1957 2,sue,943 RAILROAD IMPEDANCE BOND CONNECTION Michel Crerner and Robert Pdoussaut, Paris, France,

assignors to Forges et Ateliers de Constructions Electriques de Jeumont, Paris, France, a French body corporate Original application January 23, 1951, Serial No. 207,394. and this application April 22, 1955, Serial No.

Claims priority, application France May 8, 1950 4 Claims. (Cl. 246--37) This invention relates to impedance bonds for electrified railroad lines provided with track-circuit signalling block systems of the alternating current type, being a division of our abandoned application Ser. No. 207,304, filed January 23, 1951.

In order to separate the track circuits from adjacent sections of the track, while ensuring the free return of the traction currents through the rails, it is usual to employ impedance bonds or inductive interconnections to provide a low-resistance return path for the traction current from rail to rail at the insulated joints or spacers, while stopping the flow of track circuit alternating current between rails through the bond.

This arrangement gives complete satisfaction, so long as the insulating joints are in good condition. But it-is sometimes found that they are short-circuited partly or completely by damp, metal particles or other causes of current-leakage; in that event, the track relay controlling the signal may be prevented from dropping when the block section is shunted by a train, if, at the same time, one of the circuit connections is accidentally interrupted; in such circumstances, the relay may remain in the attracted position, in spite of the complete shunting of the block section, which will constitute a grave danger. On the other hand, means must be provided for eliminating dangerous effects of loosening or breaking of any connection in an impedance bond.

The present invention has for its object to eliminate these dangers by very simple, effective and inexpensive means which are applicable to the existing impedance bond transformers, it being possible to use this apparatus without modification; these results are obtained by a slight modification of the insulating rail joints and of the impedance bond or connector itself.

The invention is hereinafter described with reference to the accompanying drawing, in which:

Fig. l is a diagram representing an impedance-bond arrangement embodying the invention;

Fig. 2 is a face view of one of the insulating joints or spacers;

Fig. 3 is an edge View of this joint or spacer; and

Fig. 4 is a face view of a modified insulating joint or spacer.

Fig. 5 shows the conventional impedance bond arrangement.

In the well known arrangement shown in Fig. 5, two transformers T with low-tension windings for the return traction current, have the middle points of these windings joined together by means of a low-resistance bond C. The other windings of these transformers are respectively connected to a track relay Tr of one block section 12 and to a source S of alternating current, insulating joints or spacers a and b being interposed between the ends of the rails 1--3 and 2-4 of the two block sections.

If one of the insulating joints, for example the joint a, is accidentally short-circuited, as indicated at Z, the electrical energy of the alternating current source S may feed the secondary transformer winding connected to the track relay Tr, at a voltage sufiicient to prevent the dropping of this relay when the block section 1-2 is shunted by a train L; if, at the same time, one low-tension winding of that transformer is accidentally interrupted, as indicated at W, the relay Tr may remain in the attracted position, being maintained in this position by the currents shown by the arrows i, in spite of the complete shunting of the block section by the train, so that there will be a grave danger of the signals failing to respond.

Referring to Fig. 1, the arrangement comprises two transformers T1 and T2, having low-tension main windings A1B1 and A232, the midpoints of which are joined together by the conventional bond or connector C.- The secondary control winding ii of the transformer T1 is connected in series with a conventional track relay Tr, which is energized by said winding 11 and serves as usual for controlling the signals of the block section 12. The interconnection of the winding t1 and relay Tr comprises two insulated metal plates 7 and 8, which are interposed between the adjacent rails 1, 3 and 2, 4; the track relay circuit passes through the bond C connecting together the neutral or midpoints of the two main windings A1B1 and AzBz for balancing the traction return currents. The primary control Winding t2, which feeds the input transformer T2 of the block section 1-2, is connected by the leads S to a source of alternating current, current thereby induced being transmitted along the rails and through the output transformer T1 for energizing the relay Tr.

The adjacent block section 3-4 comprises asimilar source of alternating current connected to leads S, a similar input transformer T2 and a corresponding track relay (not shown) located at the opposite end of this block section.

It will be seen that the secondary control winding t1, which feeds the track relay circuit, is connected by a lead Pto one of the insulated metal plates, viz. the plate 7; the said control circuit then passes through the lead M to the neutral point Y of the winding AzBz of the input transformer T2 traverses the bond C to reach the neutral point X of the other winding A1131, thence through the lead N to the other metal plate 8, and back to the track relay by the lead Q.

To each of the insulated metal plates 7 and 8 there are attached, in the example shown, two separate leads or cables, viz. P, M and N, Q. It is preferable to fix these cables to the respective plates by means of bolts, rivets or the like or by welding in such a way that if one of the cables should become accidentally detached, it will not remain in contact with the other cable attached to the same plate, whereby the control circuit to the track relay Tr will be interrupted with certainty. For this purpose, it is suficient for example to fix the cables P and M at two difierent points on the metal plate 7, as shown in Fig. 2 or 4, the cables N and Q being similarly fixed to the other metal plate 8.

In the event of defective insulation and direct leakage of current between the rails 1 and 3, the windings A1 and A2 will be short-c rcuited; if such an insulation defect is produced between the rails 2 and 4, it will be the windings B1 and B2 that are short-circuited. In each of these cases, the alternating voltage across the two control windings t1 and t'z of both the adjacent block sections is reduced to nil, and the respective track relays drop. On the other hand, if one of the connectors P, M, C, N or Q is interrupted, the track relay Tr in the control circuit drops immediately.

It follows that any damage produces a result tending to safety and that it can be detected immediately. This is an important advantage over the known arrangements mentioned above.

.Itis to benoted that the connectors ,P, M, N and Q do not need to be of large sectional area, as they are traversed only by weak control currents. This allows aconsiderablc simplification of the cables and increases greatly the reliability of the installation, since these small connectors are not sensitive to the violent shocks produced by the rolling stock.

The practicalccnstruction of the insulated metal plates 7 and 8, interposed respectively between the rails 1, 3 and 2, 4 inFig. 1, may correspond to Figs. 2 and 3. insulationis provided by means of two thin insulating sheets and covering both faces of the metal plate. As shown in Fig. 3, the plate 7, madeof brass for example, is in terposed between two thin insulating sheets 9 and it made of synthetic resin or of fibre, for example, in order toform .a pack of a thickness f (about 8 mm. for example),iassembled by means of small rivets 13, as shown in Fig. 2, or by adhesive or in any other manner. This pack is interposed between the abutting rail ends of the adjacent block sections, as seen in Fig. l.

The shape of this insulating pacl; conforms with the profile of the rails, but, as shown in Fig. 2, its lower part is extended downwards below the bottom flange of the rails which is indicated by the line 15. The insulating sheets 9 and 10 in this embodiment have their lower corners cut off as shown, so as to leave free the parts of the metal plate '7, uponwhich the connectors M and P are respectively attached separately in any suitable mannerv According to a modification shown in Fig. 4, the downward extension of the pack can be avoided. The insulating sheets 9 and 10 have in their lower parts horizontal extensions or lugs 9' and 19', between which there are placed similar projections 7' of'the intermediate metal plate 7, the projections 7 having a greater length than the extensions or lugs 9' and 16'. In other respects the elements-9, It) and 7 have the same shape as the profile of the rails. On each side of the rails, the three superposed extensions 9', 1i?" and 7 are joined together by rivets 13; the connectors M and P are attached separately to each of the projecting ends of the metal lugs 7', as shown. The chain lines in Fig. 4 indicate the cross sections of the conventional insulated fish-plates or anglebars 1 for clamping together the two rail ends. The line 15 corresponds to the bottom flange of the rails.

It is obvious that the embodiments which have been described may be modified. It is'possible, for example, instead of connecting the insulated metal plates 7 and to the secondary control winding 11, as shown in Fig. l, to connect them to the primary control winding t'z which is energized by the supply circuit through the leads S. It is likewise possible to connect the lead M to the point X and the lead N to the point Y, or to effect in any other manner the connections between the two transformers and the insulated metal plates. The structure and the shape of the pack formed by the insulating sheets or layers and the interposed metal plates may also be difierent from that described.

What we claim is:

1. In an inductive return current interconnection for alternating current block systems having a source of alternating current and track circuits including a track relay, two conventional transformers of the impedancebond type with main windings bridged across the rails, a bond connector joining the midpoints of said windings, one of said transformers carrying a primary control winding connected to said source of alternating currentand the other carrying a secondary control winding connected to said track relay, safety means for protecting the block system against any failure of insulation or of interconnection, comprising two insulating rail spacers, each formed by two insulating sheets with a fixed metal plate therebetween, and a control circuit including said secondary control winding, a direct connection of said circuit to one of said metal plates, a direct connection between said one plate and'one end of said bond connector, a direct conne tion between th cther end of said ondconnector and the second of said metal plates, a direct connection between said second plate and the track relay, each of said metal plates being provided with two separate and spaced terminals for two of said direct connections.

2. In the art of track circuits for electrified railroads, provided with pairs of conventional impedance-bond transformers having main windings bridged across the rails, and a bond connector joining the midpoints of said main windings, one of said transformers carrying a primary control winding connected to a source of alternate ing current and the other carrying a secondary control winding connected to a track relay, two rail-spacerpaclcs each comprising two laminar insulators and a fixedmetal plate interposed between said insulators, said plate having a shape substantially the same as that of said insulators but having free parts beyond the profile of said insulators, means for assembling said plate and said insulators, separate and spaced terminals upon said free parts, a direct connection from one of said terminals upon one of said metal plates to one end of one of said bond connector, and a direct connection from one of said terminals upon the other of said metal platesto the other end of saidbondconnector, the remaining two terminals being co n cted to the r ck r l y i series with said secondary control winding, whereby any failure f said insulating rail spacers or of the circuit connections results in the dropping out of said track relay.

3. 'In the art of track circuits for electrified railroads, provided with pairs of impedance-bond transformers having main windings bridged acrossthe rails, and bond connectors joining the midpoints of said main windings, one of said transformers carrying a primary control winding connected to a source of alternating current and the other carrying a secondary control winding connected to a track-relay, a pair of insulating rail-spacers between adjaccnt-blocksections, each of said rail-spacers comprising two laminar insulators and a metal plate interposed between said insulators, said metal plates being connected directly to opposite ends of the respective bond connector, one of said metal plates being also connected directly to said track relay, and the other of said metal plates being also'connected to said track relay through said secondary control winding, whereby any failure of said insulating rail spacers or of the circuit connectionsresultsinthe dropping out of said track relay.

4. Inthe art of track circuits for electrified railroads, provided with pairs of impedance-bond transformers having main windings bridged across the rails, and bond connectors joining the midpoints of said main windings, one of said transformers carrying a primary control winding connected to a source of alterating current and the other carrying a secondary control Winding connected to a track relay, 8. pair'of,insulatingrail-spacers between adjacent'block sections, each of said rail-spacers comprising two laminar insulators'and a metal plate interposed between said insulators, each of said metal plates having two terminal lugs projecting beyond said insu lators, one terminal lug of one metalplate being connected directly to one end of the respective bond connector, one terminal lug of the other metal plate being connected directly to the other end of 'said bond connector, and the other .two terminal lugs being connected respectively to said secondary control winding and to said track relay, whereby any failure of said insulating rail spacers or of the circuit connections results in the dropping out of said track relay.

References Cited in the file of this patent V UNITED STATES PATENTS 1,181,576 na May ,2, 121.6 2,098,833 Peter Nov. 9, 1 937 7 FOREIGN PATENTS 274,433 Italy May 21, 1930 

